linux-kernel - [PATCH] powerpc/mm: Refactor the floor/ceiling check in hugetlb range freeing functions

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Message-Id: <16a571bb32eb6e8cd44bda484c8d81cd8a25e6d7.1604668827.git.christophe.leroy@csgroup.eu>
Date:   Fri,  6 Nov 2020 13:20:54 +0000 (UTC)
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH] powerpc/mm: Refactor the floor/ceiling check in hugetlb range
 freeing functions

All hugetlb range freeing functions have a verification like the following,
which only differs by the mask used, depending on the page table level.

	start &= MASK;
	if (start < floor)
		return;
	if (ceiling) {
		ceiling &= MASK;
		if (! ceiling)
			return;
		}
	if (end - 1 > ceiling - 1)
		return;

Refactor that into a helper function which takes the mask as
an argument, returning true when [start;end[ is not fully
contained inside [floor;ceiling[

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 arch/powerpc/mm/hugetlbpage.c | 56 ++++++++++++-----------------------
 1 file changed, 19 insertions(+), 37 deletions(-)

diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
index 36c3800769fb..f8d8a4988e15 100644
--- a/arch/powerpc/mm/hugetlbpage.c
+++ b/arch/powerpc/mm/hugetlbpage.c
@@ -294,6 +294,21 @@ static void hugepd_free(struct mmu_gather *tlb, void *hugepte)
 static inline void hugepd_free(struct mmu_gather *tlb, void *hugepte) {}
 #endif
 
+/* Return true when the entry to be freed maps more than the area being freed */
+static bool range_is_outside_limits(unsigned long start, unsigned long end,
+				    unsigned long floor, unsigned long ceiling,
+				    unsigned long mask)
+{
+	if ((start & mask) < floor)
+		return true;
+	if (ceiling) {
+		ceiling &= mask;
+		if (!ceiling)
+			return true;
+	}
+	return end - 1 > ceiling - 1;
+}
+
 static void free_hugepd_range(struct mmu_gather *tlb, hugepd_t *hpdp, int pdshift,
 			      unsigned long start, unsigned long end,
 			      unsigned long floor, unsigned long ceiling)
@@ -309,15 +324,7 @@ static void free_hugepd_range(struct mmu_gather *tlb, hugepd_t *hpdp, int pdshif
 	if (shift > pdshift)
 		num_hugepd = 1 << (shift - pdshift);
 
-	start &= pdmask;
-	if (start < floor)
-		return;
-	if (ceiling) {
-		ceiling &= pdmask;
-		if (! ceiling)
-			return;
-	}
-	if (end - 1 > ceiling - 1)
+	if (range_is_outside_limits(start, end, floor, ceiling, pdmask))
 		return;
 
 	for (i = 0; i < num_hugepd; i++, hpdp++)
@@ -334,18 +341,9 @@ static void hugetlb_free_pte_range(struct mmu_gather *tlb, pmd_t *pmd,
 				   unsigned long addr, unsigned long end,
 				   unsigned long floor, unsigned long ceiling)
 {
-	unsigned long start = addr;
 	pgtable_t token = pmd_pgtable(*pmd);
 
-	start &= PMD_MASK;
-	if (start < floor)
-		return;
-	if (ceiling) {
-		ceiling &= PMD_MASK;
-		if (!ceiling)
-			return;
-	}
-	if (end - 1 > ceiling - 1)
+	if (range_is_outside_limits(addr, end, floor, ceiling, PMD_MASK))
 		return;
 
 	pmd_clear(pmd);
@@ -395,15 +393,7 @@ static void hugetlb_free_pmd_range(struct mmu_gather *tlb, pud_t *pud,
 				  addr, next, floor, ceiling);
 	} while (addr = next, addr != end);
 
-	start &= PUD_MASK;
-	if (start < floor)
-		return;
-	if (ceiling) {
-		ceiling &= PUD_MASK;
-		if (!ceiling)
-			return;
-	}
-	if (end - 1 > ceiling - 1)
+	if (range_is_outside_limits(start, end, floor, ceiling, PUD_MASK))
 		return;
 
 	pmd = pmd_offset(pud, start);
@@ -446,15 +436,7 @@ static void hugetlb_free_pud_range(struct mmu_gather *tlb, p4d_t *p4d,
 		}
 	} while (addr = next, addr != end);
 
-	start &= PGDIR_MASK;
-	if (start < floor)
-		return;
-	if (ceiling) {
-		ceiling &= PGDIR_MASK;
-		if (!ceiling)
-			return;
-	}
-	if (end - 1 > ceiling - 1)
+	if (range_is_outside_limits(start, end, floor, ceiling, PGDIR_MASK))
 		return;
 
 	pud = pud_offset(p4d, start);
-- 
2.25.0